Process of making metal foils



Patents Jan. 8, 19 29.

JOHN R. CAIN, OF WASHINGTON, DISTRICT OF COLUMBIA, ASS IGNOR TO THE RICHARD- SUN COMPANY, OF LOCKLAND, OHIO, A CORPORATION OF OHIO.

rnocnss or MAKING METAL FOILS.

N0 Drawing.

My invention relates to a method of forming'metal foils on the surface of 'an electro-- produce a metal foil, capable of self-sustainment.

It is the object of my invention to be herein described to develop a technique of producing foil in this manner, and to describe those methods which apparently produce foils in a regular manner and of best characteristics.

In providing a suitable electrolyte, I have found that neutral or acid electrolytes ap pear to give best results. Otherwise the general practices of electroplating can be followed, exactly as if the desired metal were to be plated onto an electro-conductive cathode of known character, except that the current densities used in the first stage are higher than usually employed in plating.

The same holds true for the anode, and use of some heat, appearsas in electroplating generally to enhance the character of there action. I

In preparing a floating powder, I prefer either to take a clean dry powder, and treat it with benzol, which is then evaporated off without oxidizing the metal, or I may prepare the powder by precipitating it from an acid salt solution of the metal by the use of a suitable precipitant, such as a metal which will replace the metal of the salt, the acid resulting in a simultaneous productionof nascent hydrogen. The precipitated powder when washed and dried will be found to have a floating characteristic of suitable permanence, due, in my opinion to an obscure hydrogen relation to its surface. In the description that follows, 1 refer to a process using copper powder, and for other metals there will be a like practice varied according to the principles of electroplating.

In any case I prepare an aqueous electrolyte, and deposit the powder thereon from a suitable blower which spra s the dry powder over the surface, where it orms into a seemingly integral film.

The anode is placed below the surface, and

coupled to a source of current, and the other terminal is formed by a spongy metallic mass, which is touched to the edges of the floating Application filed May 3,

192a Serial No. 10 ,537.

film. A suitable blower] at one end of thetank, blowing the metal toward the other end will maintain-a film like body ,crowded against the previously deposited metal with which contact is maintained. i

I have used with success,'a current from one to two amperes per square inch, at a voltage above four volts. When a voltage oftwelve volts is used another actionis likely to take place which while apparently advantageous, has not been sulficiently investigated by me to. be recommended. I have obtained,

results with over two amperes per square inch, atthis stage, and thus do not set a limit. as to current. i

The turning on of the current results in a I I very rapid fusion like action of the particles of the metal film, which is the first stage/of my process. The use of a spongy cathode at this period is of value because it tends to prevent the formation of hydrogen in excess and thus saves the film from disruption or from being forced away from the cathode.

. Also the use of a spongy cathode prevents formation of sponge thereon and on proximate portions of the film. Where sponge forms the film is likel' to be broken followed by the'sinking thereof?- Also during this period it is advantageous to' move the cathode about. In one mechanical arrangement, the cathode can be formed with two branches one of which is moved along one side edge of a vessel containing the powdery film and one along the other edge.

As soon as the film is apparently, to the eye, welded. into an integral foil, the second stage of the process will'be started, which is nothing but a mere plating action on the welded foil.

At this stage the current densities and practice will be that found most advantageous in regular electroplating for the: metal which is to be plated onto the foil.

At this stage the practice will best be, to remove the foil from the first bath, on a suitable screen, and place it in another electrolytic bath, beneath the surface thereof, supported on the screen,-and lyin between two anodes, the foil being connected as a cathode.

When the foil is thick enough, following the second stage, it'is removed from the electrolyte by lifting out the screen, whereupon free of danger of rupture, it will be lifted-off of the electrolyte, as by a wire screen, where upon it is washed and dried.

The temperature of dryinw should be insufficient to oxidize or tarnish the foil, and after the drying operation the foil is annealed under reducing conditions, at a temperature above that of the, reduction temperature of the oxide of the metal. A final treatment by cold rolling between polished metal plates gives a fine finish to the material.

After the foil formation, and before heating and rolling, the foil will usually be dark,

and not strong, but with the final treatment it becomes quite strong, and can be used for any purpose to which foil is adapted. In some instances the foil following the second stage will be strong enough to be cold rolled without annealing.

I find that metal powders of one metal can be deposited on an electrolyte of another, such as copper on a zinc electrolyte or copper on a nickel electrolyte. In such cases the primary film is formed of the original metal on the electrolyte will float thereon, but will sink if inverted, showing that the underside of the'foil retains the floating properties of the original powder.

In the instance of the higher vbltages, heretofore referred to, the action is much more twelve volts.

rapid, and appears to show a direct platin of a foil out of the electrolyte onto the sur ace thereof which discovery I do not include in the present invention.

- Having thus described my invention, what I claim as new and desire to secure by Letters Patent, is

1. A process of forming metal foil which consists in depositing a metal powder on the surface of an electrolyte, said powder being of a nature to float thereon, and maintaining it in an integral film maintaining contact with the film formed by said powder deposition with a spongy electrode, and providing an anode, and passing an electric current through said electrode and anode. I

2. A process of forming metal foil which consists in depositing a metal powder on the surface of an electrolyte, said powder being of a nature to float thereon, and maintaining it in an integral film maintaining contact with the film formed by said powder deposition with anelectrode, and providing an anode, and passing an electric current through said electrode .and anode, said current being of an amperage of not less-than substantially one to two amperes per square inch of metal film surface being acted upon.

3. A process of forming metal foil which consists in depositing'a metal powder on the surface of an electrolyte, said powder being of a nature to float thereon, and maintaining it in an integral film maintaining contact with the film formed by said powder deposition with an electrode, and providing an anode, and passing an electric current through said electrode and anode, said current being of an amperage of not less than substantially one to two amperes per square inch of metal film surface being acted upon said current being of a voltage substantially between four and JOHN R. CAIN. 

